Dual Nature Of Matter

precisely the difference between particle and wave natures. Different scientists carried out various experiments to support this claim. For example, light may be thought of as both a wave and a particle in some circumstances. The behaviour of light as a wave is observed while viewing phenomena such as interference, diffraction, and reflection. In contrast, while studying processes such as the photoelectric effect, it is discovered that light acts as if it were a particle.

Dual Nature of Matter

According to the classical perspective, a particle concentrates energy and other qualities in space and time. In contrast, a wave is spread out over a greater region of space and time. The debate over whether light is a stream of particles (corpuscles) or a wave is a long one.

Experiments were proposed and carried out in the early nineteenth century to demonstrate that light has a wave motion. Thomas Young, one of the most intelligent and clever scientists, was a crucial figure in this endeavour, studying light diffraction and interference as early as 1803 and producing results that strongly supported Christian Huygens’ wave theory over Isaac Newton’s particle corpuscular theory.

Many other scholars also contributed, including Augustin Jean Fresnel, who demonstrated that light is a transverse wave.

According to de Broglie’s notion of matter waves, the matter has a dual nature, implying wave qualities (such as interference, diffraction, etc.) are connected while the matter moves. When it is at rest, particle attributes are linked with it. As a result, the matter has a dual nature.

Theories and Experiments Under the Dual Nature of Matter

De Broglie’s Wave

In 1924, Louis de Broglie, a French scientist, proposed that all microscopic and macroscopic things had dual nature. A matter-wave of a de Broglie wave is linked with the particle.

The wavelength of any material particle’s wave was computed as follows:

In the case of a photon, assuming it has a wave nature, its energy is given by

hv = E

where v is the wave’s frequency, and h is Planck’s constant

If the photon is thought to be a particle, its energy is given by

E = mc2

where m is the photon’s mass and c is the speed of light

Davisson and Germer Experiment

An electron gun with a tungsten filament F covered with barium oxide and heated with a low voltage power source is called an electron beam.

The electron gun releases the electrons, which are again accelerated to a certain speed by a high voltage power source.

As the electrons from the electron gun travel through a perforated tube with small holes, they will be collimated into a tiny beam and easy to point at.

Some of the electrons will be spread out in different directions because they fall on the surface of a nickel crystal again.

The intensity of the beam of electrons made will differ for each person. An electron detector is used to measure how many electrons there are. Following the connection of the galvanometer to the electron detector, the detector is moved on a circular scale to record how much electricity is flowing.

Moving the electron detector in the circular scale at different angles changes how much the scattered electron beam is detected. This is how you measure the angle or the intensity of the scattered electron beam (i.e., the angle between the incident and the scattered electron beams).

Thompson’s Experiment

A thin gold foil was used in place of the nickel crystal for this experiment, and it was a success. He discovered a diffraction pattern when an electron beam is received on a photographic plate perpendicular to the beam’s path after passing through a thin gold foil.

Photoelectric Effect

The use of light may be utilised to push electrons away from the surface of a material when the conditions are perfect. It is known as the photoelectric effect (or photoelectric emission or photoemission), and a material that exhibits this phenomenon is referred to as photoemissive. The ejected electrons are photoelectrons; however, nothing distinguishes them from other electrons in charge or charge transport. Every electron’s mass, charge, spin, and magnetic moment are equal to its counterparts.

It is impossible to understand the photoelectric effect if the light is seen as a continuous wave. On the other hand, this phenomenon may be described by the particle nature of light(dual nature of light). Light can be viewed as a stream of electromagnetic energy-bearing particles. Photons are the ‘particles’ of light that make up the visible spectrum. Planck’s equation, which describes the relationship between the energy held by a photon and the frequency of light, is as follows:

E = h𝜈 = hc/λ

Where,

E denotes the energy of the photon

h is Planck’s constant

𝜈 denotes the frequency of the light

c is the speed of light (in a vacuum)

λ is the wavelength of the light

Different frequencies of light convey photons with varied energy may be deduced. Consider that the frequency of blue light is higher than the frequency of red light (the wavelength of blue light is much shorter than the wavelength of red light). As a result, the energy contained within a photon of blue light will be more than the energy contained inside a photon of red light.

Plank’s Quantum Theory

Plank’s Quantum Theory is a theory of quantum mechanics developed by Richard Plank.

Heat causes a black body to radiate thermal radiation with varying wavelengths and frequencies depending on how hot it is. Max Planck proposed a hypothesis known as Planck’s quantum theory to explain the dual nature of radiation and matter. This theory is still in use today. In quantum theory, the most important aspects are as follows:

Continually emitting or absorbing energy in little packets or bundles of energy, substances emit or absorb energy discontinuously.

Quantum energy refers to the tiniest packet of energy. The photon is the quantum unit of light in this example.

It has been demonstrated that the energy of a quantum is precisely proportional to its frequency of radiation. In the equation,

E µ n (or) E = hn

where,

n denotes the frequency of radiation,

h denotes Planck’s constant.

Planck’s Constant= 6.626 X 10²⁷ erg – sec or 6.626 X 10^–34 J – sec, respectively.

In whole number multiples of a quantum hn, a body can emit or absorb energy in whole-number multiples of a quantum n, for example, hn, 2hn, 3hn when the positive integer is n.

Points to Remember

• A substance can contain dual nature, i.e., wave nature (exhibiting the phenomena of interference and diffraction) and particle nature [quanta/packets of light] characteristics.

• Metals contain both electrons and protons in equal quantities. Electrons are trapped inside a metal owing to the attraction forces present. However, electrons may be liberated from the metal with the assistance of an external source of energy.

• Specific procedures result in the emission of electrons from the metal surface when used in conjunction with other methods. Photo-electric Emission, Field Emission, and Thermionic Emission are some of the ways available.

• The photoelectric effect is a scientific phenomenon in which electromagnetic radiation arises on a metal surface due to the presence of the metal.

• Light energy is transformed to electric energy by the photoelectric effect, and the current produced as a result of the photoelectric effect is known as photoelectric current. Light energy is converted into electrical energy by the photoelectric effect.

Conclusion

Interference, diffraction, and polarisation are all examples of optical phenomena that demonstrate the wave nature of light from the dual nature of light.

While the photoelectric and Compton effect entails the transfer of energy and momentum, radiation behaves as if it were composed of a collection of particles-photons that demonstrate the particle character.